1. Field of the Invention
The present invention relates to a protection structure for a rod seal member of a two-port valve, which may be used in a decompression port of a vacuum chamber for employing a process gas in a semiconductor manufacturing apparatus. More specifically, the invention is directed to a protection structure for a rod seal member which is configured to prevent adhesion of by-products from the process gas to a shaft seal member or the like.
2. Description of the Related Art
In semiconductor manufacturing apparatus or the like including a flow path through which a process gas flows, a two-port valve is used for reducing a pressure in a vacuum chamber or the like, and for opening and closing the flow path. In the flow path through which the process gas is passing, by-products may be deposited readily, and connected to a poppet-shaped valve element to adhere to a sliding part of a rod for driving the valve element, thereby inhibiting opening and closing operations of the valve element. For this reason, in order to disconnect the sliding part of the rod from a hydraulic fluid, the rod is set apart from the flow path by a bellows in the prior art.
The bellows, however, may come into contact with the process gas, causing the by-products to be deposited thereon. In recent years, the deposition of the by-products in the semiconductor manufacturing apparatus has become significant, thus inhibiting the operation of the valve element, leading to fixation and thus breakdown of the bellows (see JP-B No. 3005449).
Such a problem is common among devices having the flow path through which the process gas passes, as well as a vacuum flow path of the semiconductor manufacturing apparatus.